This is a regular research subproject intended to determine the cause of chromosome-specific sensitivity to the meiotic drive system Segregation Distortion, in Drosophila melanogaster and to provide research training opportunities designed to teach a variety of techniques and analytical skills. A. SPECIFIC AIMS 1. To isolate chromosomes from nature which exhibit SD chromosome specific sensitivity. 2. To map the location of this property by recombination. 3. To identify its molecular genetic basis. 4. To analyze the Responder locus, the putative site of action of SD, on these unusual chromosomes to determine if it has been altered. 5. To determine if these natural populations harbor any molecular variants at the Segregation distorter, Sd locus. 6. To provide undergraduate research training opportunities for 2 student participants in research techniques such as stock construction and maintenance, statistical and segregation data analysis, restriction mapping, Southern analysis, subcloning and possibly DNA sequencing.